The present invention relates to a cooling control system and a cooling control method for cooling an engine of, for example, a vehicle.
Conventionally, in a vehicle engine, a cooling circuit employing a radiator is used to remove excess heat from the engine, maintain a constant operating temperature, increase the temperature in a cold engine quickly, and heat the passenger compartment. The cooling circuit includes a coolant, which is typically a mixture of water and anti-freeze (such as ethylene glycol). The cooling circuit includes a water (i.e. coolant) pump that is powered via the crankshaft of the engine, usually through a pulley and belt assembly or a gear set connected between the crankshaft and the pump, so its speed varies with the speed of the engine. The water pump forces coolant through the engine and other system components in order to prevent overheating of the engine. Also, when it is desirable to heat the passenger compartment, it pumps coolant through a heater core. When the engine is started cold, the coolant is below the optimum temperature for engine operation and it does not contain enough heat for transferring to the passenger compartment. In order to more quickly warm up such an engine system, then, a thermostat is used to redirect the flow of the coolant through a radiator bypass until the coolant is up to the desired temperature range. Once up to temperature, the coolant is routed through the radiator to assure that the temperature is maintained in the desirable range, and can be routed through the heater core to heat the passenger compartment.
In order to improve the heat transfer efficiency of the radiator, these conventional types of systems also employ a radiator fan, mounted adjacent to the radiator, to draw air through the radiator in order to better cool the coolant. The radiator fan is also typically powered via the crank shaft, so its speed is also varied as the speed of the crankshaft changes. While this conventional type of cooling system is straight forward and relatively easy to implement, it is not very good at providing the optimum cooling for the particular engine and vehicle operating conditions-particularly since the water pump and fan speed are only a function of the engine speed, not any other factors important to maintaining the desired coolant temperature.
More recently, advanced engine cooling systems have been developed that will more precisely control the engine cooling. A more advanced system may be, for example, a system and method as described in U.S. Pat. No. 6,374,780, assigned to the assignee of this application, and incorporated herein by reference. These newer systems take into account additional factors that influence both what the desired coolant temperature is and how it is achieved. Such a system might include a radiator that receives the coolant flowing out of the engine, cools the coolant and returns it to the engine; a bypass circuit for making the coolant flowing out of the engine bypass the radiator when the coolant is below the desired temperature; a fan that is driven by a motor so that its speed can be controlled to be optimum for the particular engine and vehicle conditions (independent of the engine speed); an electronically controlled flow rate control valve (or valves) for regulating the percentage of coolant bypassing the radiator; and a water pump that is either conventionally driven via the crankshaft or by an electric motor, with the electric motor controlled water pump precisely controlled to provide a desired coolant flow rate for the particular engine and vehicle operating conditions. Thus, the engine cooling system can be precisely controlled and the heating, ventilation and air conditioning (HVAC) performance optimized by controlling the coolant mass flow rate, the air mass flow rate, and the coolant flow path by one overall control strategy.
However, these advanced engine cooling systems have a drawback in that they require substantially more electric power consumption than the conventional systems. The electrically controlled valve, electrically controlled fan, and when employed, the electrically controlled water pump all draw additional electrical power.
Moreover, many additional electronic components are typically found on modern vehicles, which pushes the limit on the electrical current available from the vehicle charging system. This is particularly a concern with vehicle charging systems employing a conventional 12V electrical system rather than a high voltage system, such as 42 volts. And, in particular, pick-up trucks, sport utilities and other larger vehicles in the light vehicle class that run on 12 volts require more electrical power for the fan and water pump than typical passenger cars, so the current draw is even greater.
Thus, it is desirable to have an engine cooling system that overcomes the drawbacks of the conventional systems, while minimizing the additional electrical power needed to operate this system.
In its embodiments, the present invention contemplates a cooling system for controlling the temperature of an engine, with the engine having a rotating member. The cooling system includes a radiator, and an accessory drive adapted to be driven by the rotating member. The system also includes a fan clutch having an input member operatively engaging the accessory drive and an output member selectively engagable with the input member, and with the fan clutch electronically controllable to select the amount of engagement between the input member and the output member. A fan is located adjacent to the radiator and operatively engages the output member to be driven thereby. And, a controller actuates the clutch to thereby adjust the amount of engagement between the input member and the output member according to predetermined operating conditions.
The present invention further contemplates a method of cooling an engine, having a rotating member and a radiator, in a vehicle, the method comprising the steps of: driving an accessory drive with the rotating member; driving a fan clutch input shaft with the accessory drive; monitoring predetermined engine and vehicle operating conditions; selectively changing the degree of engagement of a fan clutch output shaft with the fan clutch input shaft based on the engine and vehicle operating conditions; and driving fan blades adjacent to the radiator with the fan clutch output shaft.
An advantage of the present invention is that an electronically controllable clutched engine cooling fan reduces the electrical power draw of a motor driven cooling fan, allowing an advanced engine cooling system to be employed without the need to greatly increase a vehicle charging system capacity.
Another advantage of the present invention is that the torque transfer to the engine fan blades can be eliminated when it is undesirable to operate the fan.
A further advantage of the present invention is that a water pump can also be driven via the crankshaft through an electronically controlled clutch in order to further reduce the electrical requirements for an engine cooling system.